This invention relates to a new and improved method for determining oil saturation in a subsurface formation surrounding a borehole by carrying out borehole gravity measurements and deep electric log measurements.
Oil fields having had a first production run using conventional production techniques and having later had a secndary production using more sophisticated production techniques are now being considered for third generation or tertiary recovery methods. These methods are naturally more expensive than the primary and secondary recovery methods. It is therefore desirable to determine the amount of residual oil left in a given field as precisely as possible so that an accurate determination of whether or not it would be economically feasible to perform tertiary recovery techniques can be made. Furthermore, the amount of residual oil is also relevant to the selection of a particular tertiary oil recovery method.